Chemical composition and bioactive properties of Cichorium spinosum L. in relation to nitrate/ammonium nitrogen ratio

BACKGROUND: Nitrogenous fertilizers may affect the yield and quality of leafy vegetables via the application rate and nitrogen form. In the present study, the effect of the nitrate:ammonium nitrogen ratio in the nutrient solution on the chemical composition and bioactive properties of Cichorium spinosum leaves was evaluated. For this purpose, C. spinosum plants were fertigated with nutrient solution containing different ratios of nitrate: ammonium nitrogen: (i) 100:0 NO₃-N:NH₄-N; (ii) 75:25 NO₃-N:NH₄-N; (iii) 50:50 NO₃-N:NH₄-N; (iv) 25:75 NO₃-N:NH₄-N; and (v) 0:100 NO₃-N:NH₄-N of total nitrogen; as well as (vi) 100% ureic nitrogen. RESULTS: The only detected tocopherol isoforms were α- and δ-tocopherol, which were positively affected by nitrate nitrogen (100:0 NO₃-N:NH₄-N). Similar results were observed for individual and total organic acids. The main detected sugars were fructose, glucose and sucrose, with a varied effect of nutrient solution composition on their content, whereas total sugar concentration was positively affected by a balanced or a slightly increased proportion of NH₄-N (50:50 and 25:75 NO₃-N:NH₄-N). The fatty acids profile was beneficially affected by the highest NH₄-N ratio (0:100 NO₃-N:NH₄-N), whereas higher amounts of NO₃ ⁻ than NH₄ ⁺ nitrogen (75:25 NO₃-N:NH₄-N) resulted in a higher content of total phenolic compounds. Finally, no cytotoxic effects were observed against non-tumor (PLP2, HeLa) and tumor (HepG2, MCF-7, NCI-H460) cell lines for any of the studied nutrient solutions. CONCLUSION: The modulation of NO₃-N:NH₄-N ratio in the nutrient solution supplied to C. spinosum may enhance the content of desirable health-promoting compounds and reduce the content of antinutrients, thus increasing the overall quality of the final product without compromising yield.